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Your Amiga, on the other hand, is a digital device; it only understands discrete occurrences of ones and zeros. To record a sound, the .Amiga needs to see it as a digital phenomenon. The answer to this problem is a device called an analog-to-digital converter (ADC). The ADC listens to a sound wave, records (“samples”) its amplitude thousands of times per second and sends these measurements to the computer as individual digital numbers. These are stored and played back later to reproduce the original sound. Figure 2 shows two examples of how an ADC might sample the various points on a simple sine wave. Once a sound is sampled, the Amiga stores the sound data in a standard file format Form 8SVX, which is a part of the IFF (Interchange File Format). The upside of this is that third-party developers have a standard around which they can design software. The downside is that 8SVX sets rigid, and not always the most musical, limits to the ways you can arrange and "loop” samples. (We’ll discuss looping in greater detail later.) One developer, Mimetics Corp., has devised its own sample format for use with the company’s Sound- Scape series. Although it increases the range and flexibility of Amiga sampling, it has not gained acceptance as a standard among other third-party developers. Amiga Sound Samplers Sound samplers (digitizers) allow you to sample your own sounds into the Amiga, edit them in various ways, and play them back. They usually consist of a small box (the ADC) that plugs into the Amiga's parallel (printer) port, and some sample-editing software. Two solid performers in the field are Datel Utilities' Pro Sampler Studio and SunRize Industries’ PerfectSound. Each stores its samples in the standard, IFF format. Through its left and right inputs, Perfect- Sound will sample stereo sounds at up to a 25 kHz sampling rate. Datel’s ADC which includes a microphone pre-amp uses one of its three mono inputs (' 4-inch mic, line level, and 5-pin mic), leaving the stereo channelizing up to its software, and takes samples at rates up to the Amiga’s maximum Direct Memory Access rate of 28,867 kHz. The principal strength of Datel’s sample-editing software is its looping feature. (To conserve memory, the final portion of a sample is often “looped” played over and over to create a sustained sound. Determining the points in a sample where to begin and end a loop is an art requiring patience, skill, and good editing software.) PerfectSound, on the other hand, excels at transposing samples and arranging them across pitch ranges to create musical instruments. Both packages allow you to sample a sound, trim off any unwanted parts, and store it for later playback. Because both follow the Amiga standard IFF format, most programs using Amiga samples can access the sounds you create with either sampler. SunRize Industries also offers a separate sample- editing program, StudioMagic (S99.95), which can be substituted for the software packaged with PerfectSound or used with other samplers. It affords more sophisticated editing features, and it allows you to play IFF samples (along with MIDI-produced sounds) from the keyboard of an optional MIDI- connected synth, splitting it into secdons. FutureSound (Applied Visions) is another sound sampler wTith excellent editing software that allows you to vary sampling rates, combine and swap sections of four resident samples, and graph sound waves. Two new samplers, A.M.A.S. Advanced MIDI Amiga Sampler (Microdeal MichTron) and ProSound Design (Precision) have recently arrived on the market. Both include sample-editing softw-are and provide MIDI support. A related package, Aegis’ AudioMaster II, is actually only editing software there is no ADC included but it can be used with samplers from other manufacturers (both PerfectSound and Pro Sampler Studio work fine) or it can load already sampled files. AudioMaster II can use Amiga expansion RAM for larger samples (which allow for higher sampling rates and thus better sound quality, and for stereo sampling, which doubles the file size).